A handout photo from 2004 shows coastal erosion of mud-rich permafrost along on Beaufort Sea coastline Drew Point in Alasaka.(Xinhua/Reuters Photo)Photo Gallery>>>

WASHINGTON, Sept. 1 (Xinhua) -- The thawing of
permafrost in northern latitudes, which greatly increases microbial
decomposition of carbon compounds in soil, will dominate other effects of
warming in the region and could become a major force promoting the release of
carbon dioxide and thus further warming, according to a new assessment in the
Sept. issue of BioScience.

The study, by an international team of researchers,
more than doubles previous estimates of the amount of carbon stored in the
permafrost: the new figure is equivalent to twice the total amount of
atmospheric carbon dioxide.

The authors conclude that releases of the gas from
melting permafrost could amount to roughly half those resulting from global
land-use change during this century.

Researchers refine earlier assessments by considering
complex processes that mix soil from different depths during melting and
freezing of permafrost, which occur to some degree every year.

They judge that over millennia, soil processes have
buried and frozen over a trillion metric tons of organic compounds in the
world's vast permafrost regions.

The relatively rapid warming now under way is
bringing the organic material back into the ecosystem, in part by turning over
soil, said the researchers.